354 SPECIAL HISTOLOGY. 



The proper cornea, or the fibrous layer (fig. 296 c), by far 

 the most important part of the whole tunic, consists of a fibrous 

 substance closely allied to connective tissue, but which, accord- 

 ing to J. Miiller, affords when boiled, not gelatin, but chondrin. 

 Its elements, pale bundles, 0*002 — O'OO^" in diameter, in 

 which, at least when teazed out, finer fibrils are usually per- 

 ceptible, sometimes more and sometimes less distinctly, are 

 united into flat bundles. These bundles, which have their 

 flat sides always parallel with the surface of the cornea, decussate 

 in various directions, and exhibit, if not complete lamellae, 

 yet a distinctly laminated structure, owing to which the cornea 

 is very readily torn and penetrated in the direction of its sur- 

 faces, and with great difficulty in that of its thickness. The 

 correspondence of the corneal elements with connective tissue 

 is also shown by the following circumstances : 1. that it is con- 

 tinuous at the border, by its elements, which in that situation 

 follow principally a radiating direction, directly and without in- 

 terruption with the similarly disposed fibres of the sclerotic, so 

 that there cannot be the least question as to the non-existence 

 of any natural demarcation between the two tunics ; and 2. as 

 Virchow was the first to show, that a great number of anas- 

 tomosing, fusiform and stellate., nucleated cells lie among its 

 bundles, just as they do in undeveloped elastic tissue (connec- 

 tive tissue-corpuscles of Virchow), which also exist in the 

 sclerotic, though more branched. It can perhaps scarcely 

 be doubted, that the nutritive fluid, with which the cornea is 

 constantly imbued in considerable quantity, and which, in the 

 large eyes of animals, may be directly demonstrated by expres- 

 sion, is in great measure conveyed and distributed in the in- 

 terior, by the cells in question ; a view which is only strengthened 

 by the knowledge that these cells, in morbid conditions of the 

 cornea, very frequently contain oil-drops, and occasionally, ac- 

 cording to Donders, even pigment, in their interior. The 

 u corneal tubes" injected by Bowman in the eye of the Ox and 

 in that of Man must not be confounded with this cellular 

 network, and are probably to be explained as artificial dilata- 

 tions of the minute interstices which normally exist between the 

 structural elements of the cornea, and which it is thought may 

 occasionally be perceived on microscopical examination. 



The conjunctival membrane of the cornea (fig. 296 a, b) is 



